Abstract/Summary

We consider the likely levels of solar activity in 2100 by analysing the previous history of long-term solar and geomagnetic activity indices. We make use of superposed periods of similar variations in atmospheric cosmogenic radiocarbon that have occurred during the last 11000 years, as derived from various proxies such as tree rings. This leads us to conclude that solar activity is peaking at about the present epoch, and we expect solar activity in 2100 to resemble that in 1900 when a small minimum in solar activity took place, rather than increasing as has occurred in the last 100 years. The occurrence of major geomagnetic storms will decline to about one-third of the present level.